1. Field of the Invention
The present invention relates to a cleanroom and a method for ventilation of a cleanroom, and more particularly to a cleanroom and method for ventilation of a cleanroom for use in the process of manufacturing a semiconductor device, and particularly a cleanroom and cleanroom ventilation method for providing localized cleaning of dust, impurities, and chemical substances of air in a contaminated region.
2. Background of the Invention
In a process for manufacturing a semiconductor device of the past, a cleanroom is generally used to prevent contamination of a wafer by dust and other impurities or chemical substances or the like in the air, thereby preventing a worsening of the characteristics of the final product and the occurrence of failed products.
A cleanroom 1 of the past, as shown in FIG. 3, is often made up by an outer chamber 20 and an inner chamber 10, and within the inner chamber 10 are provided a semiconductor production apparatus 2, a movable interface box 4 containing wafers 3 that are to be processed by the semiconductor production apparatus 2, and an interface box opener 5 mounted in a fixed manner to the interface box 4, which transports wafers 3 to within the production apparatus 2 from within the interface box 4. In the interface box type cleanroom 1, an integral fan-filter unit (hereinafter referred to as an FFU) 7 made up of a fan 8 and a filter 9 is installed at the top part of the interface box opener 5 in the inner chamber 10, a chemical filter 6 being further installed at the top of the FFU 7, wherein after removing specific components from the atmosphere within the inner chamber 10 of the cleanroom 1, a clean air flow is introduced into the interface box opener 5.
External air supplied form an external air adjusting apparatus 14 is first introduced into an air circulation path formed between the inner chamber 10 and the outer chamber 20, and via FFU 7 configured as noted above disposed at a prescribed spacing therebetween on the ceiling of the inner chamber, this air is introduced into the inner chamber 10, the air having been introduced into the inner chamber 10 then circulating from exhaust holes 28 provided in the floor 40 of the inner chamber 10 to an air circulation path 12, thereby circulating in the above-noted flow path.
In the present invention, the above-noted air flow will be referred to as the first air flow.
An appropriate air cooling means 17 can be provided inside the air circulation path 12, and further, because of the need to monitor the external air pressure of the cleanroom 1 and the internal air pressure of the inner chamber 10 with a sensor 16 and a detector 15 and to make the air pressure within the inner chamber 10 be greater than the external air pressure by a prescribed amount at all times, the difference between the air pressures is detected as noted above and, then the pressure difference falls below a prescribed pressure, an external air adjustment apparatus 14 is driven, so as to introduce external air into the air circulation path 12.
Control is performed so as to mix external air upstream of the FFU 7, the amount thereof being controlled so that the difference between the pressure within the cleanroom and the external chamber is maintained constant.
In the prior art, in order to perform localized cleaning of the air in a region that includes the interface box opening 5 that removes a wafer held within the interface box 4, in which there is a high possibility of contamination of the wafers 3 within the cleanroom 1, a hole was formed in the cover of the interface box 4, and an FFU 7 was provided separately from the FFUs on the ceiling of the inner chamber 10, a chemical filter 6 being provided in the FFU 7 to clean this air flow.
However, chemical substances, and particularly organic components used in processing that can scatter within the cleanroom can be included in the circulating air, and in processing even organic components that are singularly not a problem during processing, due to a catalytic action of chemical filter attraction agents and activated charcoal, break down, causing the occurrence of byproducts.
For example, even chemical substances used in the semiconductor device manufacturing processes are broken down by, for example, the catalytic action of the phosphoric acid attraction agent of the activated-charcoal chemical filter or activated charcoal, and depending upon the concentration thereof, these could influence a semiconductor device manufacturing process.
In the above-noted prior art, there is a possibility that the above-noted components intrude into the interface box opener 5, and when the opener of the interface box 4 is opened and closed, there is a possibility of being pulled into the atmosphere thereof, thereby adversely affecting the wafers 3 therein.
Then, some relevant prior art references will be explained as follows.
In the Japanese Unexamined Patent Application publication H4-80538 as a first reference, there is disclosure of a cleanroom using a removal filter that operates only when there is a leak of a chemical or gas or the like within the cleanroom.
The first reference intends to prevent medicine mist, etc., from being diffused into a clean room by mounting a detriment removing agent in an air conditioner return port, normally bypassing circulating air, switching a shutter at the time of leakage of medicine, etc., and passing it through a detriment removing agent filter. Nevertheless, there is no disclosure of technology for locally exposing a specific location within the cleanroom to a clean air flow.
In the Japanese Unexamined Patent Application publication H7-45581 as a second reference, a semiconductor substrate chemical treater is disclosed, which reduces the amount of the air to be fed for maintaining the cleanness of a chemical treating part in a semiconductor substrate chemical treater, and to miniaturize the scale of an air-handling system for air feed. Nevertheless, in the second reference, there is only disclosure of a configuration using an air flow for preventing the evaporation and scattering of a processing chemical in a semiconductor device processing apparatus, but no disclosure of technology for locally exposing a specific location within the cleanroom to a clean air flow.
In the Japanese Unexamined Patent Application publication H9-148294 as a third reference, a substrate processor is disclosed, which is directed to efficiently supply down flow and to reduce running cost by effectively using exhaust which does not contain chemical, In the third reference, there is only disclosure of a method of circulating an air flow and use of a filter within a cleanroom, but no disclosure of technology for locally exposing a specific location within the cleanroom to a clean air flow.
In addition, in the Japanese Unexamined Patent Application publication H10-238833 as a fourth reference, there is disclosure of a cleanroom having the usual configuration, wherein, during maintenance of part of the production equipment, a movable dividing wall is provided above this part of the production equipment hung from above, simultaneously with the supply of a separate clean air flow within the dividing wall.
However, in the above known example, a considerable large region, including the production equipment, is delineated by the dividing wall, clean air being introduced to therewithin, this apparatus being configured so as to be movable and moved only with respect to production equipment requiring maintenance, stopped at the position thereof, and used to introduce clean air flow thereto, thereby making the apparatus large and requiring it to be operated continuously.
Accordingly, in order to improve on the above-noted drawbacks in the prior art, it is an object of the present invention to provide a low-cost cleanroom and method for ventilating a cleanroom, which greatly reduce the possibility of wafer contamination, and can be expected to improve both semiconductor device quality and yield.
In order to achieve the above-noted object, the present invention has the following technical constitution.
Specifically, a first aspect of the present invention is a cleanroom configured by an inner chamber inside of which are disposed prescribed semiconductor device production equipment, a movable interface box with a plurality of wafers therewithin, and an interface box opener, fixed on the interface box, which transports wafers to within the production equipment from within the interface box, and an outer chamber which surrounds the inner chamber, and which forms an air circulation path between itself and the inner chamber, wherein air inside the inner chamber circulates in the air circulation path via a fan filter unit provided in the inner chamber, a clean second air flow, independent from the first air flow circulating in the inner chamber and air circulation path, being directly supplied to a region near the interface box opener from the outside of the cleanroom.
A second aspect of the present invention is a method for ventilating a cleanroom configured by an inner chamber inside of which are disposed prescribed semiconductor device production equipment, a movable interface box with a plurality of wafers therewithin, and an interface box opener, fixed on the interface box, which transports wafers to within the production equipment from within the interface box, and an outer chamber which surrounds the inner chamber, and which forms an air circulation path between it and the inner chamber, whereby air inside the inner chamber circulates in the air circulation path via a fan filter unit provided in the inner chamber, a clean second air flow, independent from the first air flow circulating in the inner chamber and air circulation path, being directly supplied to a region near the interface box opener from the outside of the cleanroom.
By adopting the above-noted technical constitution, a cleanroom and cleanroom ventilation method according to the present invention, when a part at which a wafer in the interface box is exposed to the atmosphere in the cleanroom, for example, a part of the interface box opener, is subjected to a flow of air from a chemical filter, to remove a chemical, air from which an impurity has been selectively removed by the chemical filter is supplied to part of the interface box, localized xe2x80x9call-freshxe2x80x9d ventilation being done, in which temperature-adjusted outside air is directly introduced into the chemical filter, thereby removing the influence of broken down substances in the chemical filter from components in the cleanroom atmosphere. By making secondary use of part of the air that has passed through the interface box opener for the purpose of pressurizing the cleanroom, and limiting the all-fresh ventilation to the interface box opener part, it is possible to enable an all-fresh ventilation function without having to providing all-fresh ventilation throughout the entire cleanroom, thereby resulting in an energy savings.